Vehicles such as loaders are used generally to transfer bulk material from a stock pile onto transport vehicles such as trucks or railroad cars. In such vehicle loading applications, the loader performs a series of functions including: digging and/or crowding a stock pile, racking back the bucket to maintain the load, travelling to a dump site or a transport vehicle while raising the bucket, and finally dumping the load from a raised position.
Various devices used on such loader vehicles, such as payload monitors, productivity indicators, and suspension monitors, typically monitor an operational parameter of one or more hydraulic cylinders. The characteristics of the sensed parameters are often dependent on which function in the loading operation is being performed. As a result, these devices must have an indication of which function is being performed in order to know how the sensed parameter is expected to behave.
In the case of payload monitors, it is generally the lifting phase that is of the greatest interest. During the lifting phase, the lift cylinder pressure versus time characteristic can be represented by a second order polynomial whereas during the digging phase there is no identifiable relation between the payload in the bucket and the sensed parameters. In productivity indicators, the length of time during which each of the functions is performed is of interest to a loading site manager. Suspension monitors are most capable of providing accurate indications of the suspension performance or the road surface characteristics during the roading function.
Some prior art systems have used hall effect sensors to detect the implement being at a predetermined location while others have included operator interfaces to allow the operator to indicate when a function of interest is being performed. Both of these methods are disadvantageous because they do not indicate all of the functions in the loading cycle or because they disrupt the loading operation, or both. The hall effect method produces inaccurate results if the bucket is not raised above the predetermined location. The operator interface method increases the operator's work load and can produce inaccurate results if the operator is not diligent in indicating the proper function.
A payload monitor disclosed in U.S. Pat. No. 4,919,222 issued to Kyrtsos et al. on Apr. 24, 1990 includes an apparatus for identifying a lifting function by sensing the extension of the lift cylinder and comparing the sensed extension to a number of predetermined constants. While this device provides an accurate indication of the lifting function, it could be improved by making it operable with systems which sense hydraulic pressure only. In addition, the disclosed embodiment does not identify any of the other functions in the loading operation.
The present invention is directed to overcoming one or more of the problems set forth above.